have you tried driving it with the driveshaft out of the vehicle to eliminate it as a source of your vibration?
no, didn't no if i could.
yes. you can remove the driveshaft and still drive it. It would just be a front wheel drive vehicle but will help in the diagnosis.
how can i exsplain this to my dealer so i can finally get it fixed.
Idrive this element over 600 highway miles a week, i need some help
I do not think they are going to want to drive it over the legal speed limits to verify if it is the driveshaft. Since this has been an ongoing concern you may want to speak to the service manager and explain your situation. Hopefully he will then have one of the technicians remove the driveshaft and let you drive it to see if the vibration goes away or not.
what else could it be if it's not the drive shaft?
this doesn't seem to be a common problem with the vehicle
motor or transmission mount?
No it is not a very common problem at all. motor mounts normall cause idle vibrations more than vibrations while driving
I have seem a couple inner C/V joins start binding and those normally cause a vibration while accelerating.
but this vibbation is very consistant and progresses with speed
That is why I do not think it a C/V joint, but you may be correct in thinking it is the driveshaft.
how about the u joint installation
The u-joints are not serviceable at least at the dealership level. they could be binding which is another reason it needs to be driven with the driveshaft out.
Any other words of wisdom for me, you know this is my 4 th element.
I am glad to hear you like the Elements,too bad this is supposed to be the last year for them.
I still think you are on the right track with the driveshaft.